1. Field of the Invention
This invention relates to a furnace for providing heated circulation air to an interior comfort space, and is more particularly directed to a condensate trap for a multi-poise forced air furnace of the type having a heat exchanger.
2. Description of the Prior Art
In conventional gas-fired forced air furnaces a thermostat senses the temperature in the comfort zone relative to a predetermined set point temperature. When the temperature is below the set point, the thermostat closes to supply thermostat ac power to the furnace as a call for heat. This initiates a sequence of events that ultimately causes the furnace to come on. An inducer motor is enabled to flow combustion air across the burners, and through a condensing heat exchanger, after which a gas valve is actuated to supply gas to the gas burners. An ignition device is also actuated to light the burners. A flame sensor then proves burner ignition and sends power to a burner delay timer. Then after a predetermined blower delay time, which varies with furnace design, the furnace blower is actuated. The blower moves circulating room air from a return air duct through the furnace heat exchanger to pick up heat from the heated combustion products (carbon dioxide and water vapor) from the gas burners. The heated circulate air then goes into a hot air plenum and is distributed through hot air ductwork back to the comfort space. When the comfort space air is warmed sufficient to reach the thermostat set point, the thermostat terminates the call for heat. When this happens the blower and burners go through a shut off sequence and the furnace awaits the next call for heat.
The present invention mainly deals with handling of large amounts of condensate that form in the condensing heat exchanger and also in the inducer. When the inducer motor is in operation a substantial step-up in pressure occurs between the condensing heat-exchanger and intake of the inducer on the one hand, and the outflow of the inducer on the other hand. Typically there is negative pressure (relative to atmospheric pressure) at the intake, and positive pressure at the outflow.
Older furnaces typically create positive pressure of about 11/2 inches (3.8 cm) of water, and negative pressure of about 21/2 inches (6.3 cm) of water, so that the trap only had to be 4 inches (10.2 cm) tall. Modern high flow furnaces can produce about 4 inches (10.2 cm) of positive pressure and 4 inches (10.2 cm) of negative pressure, requiring the trap to be at least 8 inches (20.3 cm) tall. An improved dual-sided condensate trap, which has reduced vertical height, is disclosed in my copending application Ser. No. 100,615, now U.S. Pat. No. 5,309,890.
Modern furnaces, such as forced air gas-fired condensing furnaces, are designed for multipoise applications. It is essential that the condensate trap operate in many supply air flow directions, i.e., upflow, downflow, horizontal left and horizontal right applications.